According to a 1955 St. Joseph Daily Missal with Francis Cardinal Spellman as the Imprimatur, page 642 for The Ordinary of the Mass says, all between p.642-703 are the unchangeable parts of the mass–do you disagree?

I don’t have a copy of that missal, but the Ordinary part of the Mass is that part the doesn’t change from day to day, regardless of the importance of the day. There are other parts that are subject to change every day such as the Opening Prayer, the Prayer over the Gifts, the Prayer After Communion . The Gloria is only said on Sundays, solemnities and feasts.

But actually through the centuries the whole Mass, including the Ordinary has changed many times. Of course, the essentials always remained even though the non essentials evolved. For more on the history of the Mass, see this article from the Original Catholic Encyclopedia: %between%
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*]Liturgy of the Mass[/LIST]Fr. Vincent Serpa, O.P.